OPERATION REDWING Project 2.62a Fallout Studies by Oceanographic Methods, 1961, WT-1316

Determines the fallout dose rate and first two-day dose contour areas for open land areas (no shielding) for the 1956 nuclear weapon tests:

Zuni (3.53 Mt, 15% fission, lead pusher; coral island surface burst)

Tewa (5.01 Mt, 87% fission, U238 pusher; coral reef burst with very shallow water)

Flathead (365 kt, 73% fission, gold "salted" pusher to enhance initial radiation of refractory or fast-condensing large close-in fallout particles with radiation from 2.7 days half life gold-198; barge burst in relatively deep water at Bikini Lagoon)

Navajo (4.5 Mt, 5% fission, lead pusher; barge burst in relatively deep water at Bikini Lagoon)

Note that Figure 2.45 shows that there is very little difference if any in these downwind fallout areas for the land and water surface bursts, so that the fallout areas can be directly compared for the different degrees of "cleanness" of the weapon designs.  For example in Table 2.11 it is shown that the lethal outdoor 1000 R two-day dose contour for an equivalent land surface covered only 20 square miles for the 5% fission, 4.5 Mt Navajo test, as compared to 520 square miles for the same dose from the 87% fission 5.01 Mt Tewa test.

This indicates that the popular objections to "clean" thermonuclear weapons are merely specious propaganda, and that most of the fallout threat can indeed be eliminated with minimal effects to weapon performance by simply using a lead pusher in place of U238 in weapons, since for the 14 MeV neutrons from T + D fusion, the cross-section for the (n,2n) reaction in lead is higher than it is in beryllium, and lead is not therefore inert but helps to fission lithium, releasing further tritium and aiding the efficiency of the fusion thermonuclear reaction.

Data from Castle report WT 915 indicates the limited area of upwind fallout dose rates do differ between land and surface bursts, being about 10 times lower for ocean surface bursts than for land surface bursts.  However, the same report shows that the particle size distributions of the fallout from land and surface bursts are relatively similar, contrary to claims made in Redwing report WT 1317 which sampled very small fallout sizes from fallout arriving several hours after water surface bursts and misleadingly compared that data to the larger fallout particle sizes arriving within one hour from land surface bursts.  In reality, the fallout particle size distribution from both land and water surface bursts is a function of time of sampling, so that the average size of particles arriving decreases with time after burst.  Once this factor is allowed for, there is no significant difference between the sizes of fallout particles from the Redwing land and surface bursts in the main downwind fallout areas.